1. Field of the Invention
The present invention relates to a bus bar structure stored in an electric junction box which laser welding is optionally used.
2. Description of the Related Art
Conventionally, the following welding technique has been proposed (see Japanese Unexamined Patent Application No. 2-103876 opened in 1990). That is, as indicated in FIG. 13A, a laser beam LB is irradiated onto a crimp-style portion 3a of a crimp-style terminal 3 for crimping/connecting a conductor 2 of an electric wire (electric cable) 1, and thus both the crimp-style portion 3a and the conductor 2 are melted to thereby be welded with each other.
Another conventional welding structure has been proposed (see Japanese Unexamined Patent Application No. 6-302341 opened in 1994). As illustrated in FIG. 13B, a metal projection portion 5 used to fill a melting volume is separately provided with a plate-shaped welding metal conductor portion 4, a conductor 2 constituted by a plurality of base lines 2a is arranged under this projection portion 5, and then a laser beam LB is irradiated onto the projection portion 5, so that the projection portion 5 is melt with the conductor 2 to thereby be welded with each other.
On the other hand, an electric junction box used to branch/connect an automobile wire harness and the like to various electric equipments is employed so as to concentrate branch connection points to a single point, so that electric wires, or cables are branched/connected to each other in view of rational and economical aspects. Since wire harnesses are made in higher density, various types of wire harnesses have been developed, depending upon sorts of automobiles, or utilizations in automobiles.
As the above-described electric junction box, as represented in FIG. 12, the following electric junction box has been proposed. That is, bus bars 7A to 7C are stamped from a hoop member 6, respectively, by using a press die, or a press metal mold. Tab terminals 7a and 7b are cut out from pattern portions of the respective bus bars 7A to 7C to be raised. Also, electric insulating plates 8A to 8C are interposed between the respective bus bars 7A to 7C so as to be stacked. The stacked members are stored into an upper case 9A and a lower case 9B of the electric junction box 9.
The tab terminal 7a cut/raised along the upper direction from the bus bar 7B located at the middle layer among the above-explained respective bus bars 7A to 7C is set in such a manner that this tab terminal 7a penetrates the insulating plate 8A of the upper layer, and the height of this penetrating tab terminal 7a is made equal to that of the tab terminal 7a which is cut/raised along the upper direction from the bus bar 7A of the upper layer, as shown in FIG. 11 in detail. Furthermore, the tab terminal 7a cut/raised along the upper direction from the bus bar 7C located at the lower layer is set in such a manner that this tab terminal 7a penetrates both the insulating plate 8B of the middle layer and the insulating plate 8A of the upper layer, and the height of this penetrating tab terminal 7a is made equal to that of the tab terminal 7a which is cut/raised along the upper direction from the bus bar 7A of the upper layer.
Similarly, the tab terminal 7b cut/raised along the lower direction from the bus bar 7B located at the middle layer is set in such a manner that this tab terminal 7b penetrates the insulating plate 8C of the lower layer, and the height of this penetrating tab terminal 7b is made equal to that of the tab terminal 7b which is cut/raised along the lower direction from the bus bar 7C of the lower layer. The tab terminal 7b cut/raised along the lower direction from the bus bar 7A located at the upper layer is set in such a manner that this tab terminal 7b penetrates both the insulating plate 8B of the middle layer and the insulating plate 8C of the lower layer, and the height of this penetrating tab terminal 7b is made equal to that of the tab terminal 7b which is cut/raised along the lower direction from the bus bar 7C of the lower layer.
Then, as shown in FIG. 12, a fuse 11 and a relay 12, which constitute external parts, are inserted via a junction terminal 10 and the like, and connected to the respective tab terminals 7a and 7b. Also, a connector externally provided on an integration side is directly inserted and connected to these tab terminals 7a and 7b.
In such a case that a circuit volume installed in the electric junction terminal box 9 is increased, the pattern portions located close to the bus bar 7A (7B, 7C) in the same layer may be connected to each other by way of connectors, the pattern portions of the bus bars 7A to 7C in the different layers may be connected with each other by using connectors, and furthermore, other electric distributing materials (namely, conductors such as FPC, PCB, and electric cable) may be connected to the pattern portions of the bus bars 7A to 7C by employing connectors.
On the other hand, very recently, the below-mentioned trial has been made. That is, a plurality of electric junction boxes mounted inside an automobile in a distribution manner are intensively collected to constitute a single electric junction box, and this single electric junction box is arranged in a center cluster and the like. As a consequence, a total number of wire harnesses used to connect the respective electric junction boxes with each other is reduced, or simplified.
In the case that a total quantity of circuits provided in the above-described electric junction boxes is on the order of 40, the above-explained bus bar stacked layer structure made of the three layers may be employed. However, if a total number of circuits employed in the electric junction boxes is increased up to 80 to 100 approximately by way of the above-described intensive collection of these electric junction boxes, then a bus bar stacked layer structure made of 8 to 10 layers is constructed.
When such a bus bar stacked layer structure made of 8 to 10 layers is constructed, the lengths of the tab terminals must be made longer than those of the above tab terminals, by which these long tab terminals may penetrate 8 to 10 layers of the insulating plates at maximum. That is, when the tab terminals are cut/raised along the upper/lower directions from the pattern portions of the bus bars of the respective layers, the tab terminal cut/raised from the bus bar of the uppermost layer along the upper direction must be set in such a manner that the height of this tab terminal is made equal to that of the tab terminal cut/raised from the bus bar of the lowermost layer along the upper direction.
However, in order that the long tab terminals are cut/raised from the pattern portions of the bus bars, since spaces used to cut/raise these long tab terminals are required in the pattern portions, these spaces will constitute a so-called "dead space". Accordingly, since the resultant bus bars cannot be made compact, but also in high density, there is a problem that a total number of bus bar stacked layers cannot be lowered.